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''Zostera'' is a small
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of widely distributed
seagrass Seagrasses are the only flowering plants which grow in marine (ocean), marine environments. There are about 60 species of fully marine seagrasses which belong to four Family (biology), families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and ...
es, commonly called marine eelgrass, or simply seagrass or eelgrass. The genus ''Zostera'' contains 15 species.


Ecology

'' Zostera marina'' is found on sandy substrates or in
estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...
, usually submerged or partially floating. Most ''Zostera'' are
perennial In horticulture, the term perennial ('' per-'' + '' -ennial'', "through the year") is used to differentiate a plant from shorter-lived annuals and biennials. It has thus been defined as a plant that lives more than 2 years. The term is also ...
. They have long, bright green, ribbon-like leaves, the width of which are about . Short stems grow up from extensive, white branching
rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...
s. The flowers are enclosed in the sheaths of the leaf bases; the fruits are bladdery and can float. ''Zostera'' beds are important for sediment deposition, substrate stabilization, as substrate for epiphytic
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
and micro-invertebrates, and as nursery grounds for many species of economically important fish and shellfish. ''Zostera'' often forms beds in
bay mud Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuary, estuaries, which are normally in temperate regions that have experienced cyclic ...
in the estuarine setting. It is an important food for brant geese and wigeons, and even (occasionally)
caterpillar Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder ...
s of the grass moth '' Dolicharthria punctalis''. The slime mold '' Labyrinthula zosterae'' can cause the wasting disease of ''Zostera'', with ''Z. marina'' being particularly susceptible, causing a decrease in the populations of the fauna that depend on ''Zostera''. ''Zostera'' is able to maintain its
turgor Turgor pressure is the force within the cell that pushes the plasma membrane against the cell wall. It is also called ''hydrostatic pressure'', and is defined as the pressure in a fluid measured at a certain point within itself when at equilib ...
at a constant pressure in response to fluctuations in environmental osmolarity. It achieves this by losing solutes as the tide goes out and gaining solutes as the tide comes in.


Distribution

The genus as a whole is widespread throughout seashores of much of the Northern Hemisphere as well as
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
,
New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...
,
Southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...
and southern
Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
. The discovery of '' Z. chilensis'' in 2005 adds an isolated population on the Pacific coast of
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
to the distribution. One species ('' Z. noltii'') occurs along the land-locked
Caspian Sea The Caspian Sea is the world's largest inland body of water, described as the List of lakes by area, world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, ...
.


Uses

Eelgrass has been used for food by the Seri tribe of Native Americans on the coast of
Sonora Sonora (), officially Estado Libre y Soberano de Sonora (), is one of the 31 states which, along with Mexico City, comprise the Administrative divisions of Mexico, Federal Entities of Mexico. The state is divided into Municipalities of Sonora, 72 ...
, Mexico. The rhizomes and leaf-bases of eelgrass were eaten fresh or dried into cakes for winter food. It was also used for smoking deer meat. The Seri language has many words related to eelgrass and eelgrass-harvesting. The month of April is called ''xnoois ihaat iizax'', literally "the month when the eelgrass seed is mature". ''Zostera'' has also been used as packing material and as stuffing for mattresses and cushions. On the Danish island of Læsø it has been used for thatching roofs. Roofs of eelgrass are said to be heavy, but also much longer-lasting and easier to thatch and maintain than roofs done with more conventional thatching material. More recently, the plant has been used in its dried form for insulation in eco-friendly houses and as a ground cover in permaculture gardens, once its salt layer washed off (ex: Friland, Danish eco-village). In the United States, eelgrass insulation was commercially marketed in the early 1900s as Cabot's Quilt by the Samuel Cabot Co of Boston. However, due to an outbreak of '' Labyrinthula zosterae'' which destroyed crops of eelgrass, combined with the collapse of the homebuilding industry due to the great depression, it went out of production and was replaced in new homes with fiberglass (introduced in the late 1930s). Some studies show promise for eelgrass meadows to sequester atmospheric carbon to reduce anthropogenic climate change. ''Zostera'' can also be utilized to produce biomass energy using the Jean Pain method.


Species

;Accepted species * '' Zostera asiatica'' Miki – Russian Far East, Japan, Korea, NE China * '' Zostera caespitosa'' Miki – Russian Far East, Japan, Korea, NE China * '' Zostera capensis'' Setchell – Madagascar; Kenya to Cape Province * '' Zostera capricorni'' Ascherson – New Guinea, Australia, New Zealand * '' Zostera caulescens'' Miki – Russian Far East, Japan, Korea, NE China * '' Zostera chilensis'' (J. Kuo) S. W. L. Jacobs & D. H. Les – Chile * '' Zostera japonica'' Ascherson & Graebner – Russian Far East, Japan, Korea, China, Vietnam * '' Zostera marina'' L. – shores of North Pacific, North Atlantic, British Isles Mediterranean, Black Sea, Sea of Okhotsk * '' Zostera mucronata'' den Hartog – Australia * '' Zostera muelleri'' Irmisch ''ex'' Ascherson – Australia * '' Zostera nigricaulis'' (J.Kuo) S.W.L.Jacobs & D.H.Les – Australia * '' Zostera noltii'' Hornem. – shores of Northeastern Atlantic, Mediterranean, Black Sea, Caspian Sea * '' Zostera novazelandica'' Setchell – New Zealand * '' Zostera polychlamys'' (J.Kuo) S.W.L.Jacobs & D.H.Les – Australia * '' Zostera tasmanica'' Martens ''ex'' Ascherson – Australia


References


External links


Flora Europaea: ''Zostera''

Flora of North America: ''Zostera''

Flora of China: ''Zostera'' species list





Long Island's Seagrass conservation website, Seagrass.LI
{{Authority control Alismatales genera Biota of the Atlantic Ocean Flora of the Pacific Biota of the Indian Ocean Biota of the Caspian Sea Salt marsh plants Taxa named by Carl Linnaeus